The present invention relates to a device for introducing a secondary gas, including but not limited to blowby gas, EGR gas and/or secondary air, into the intake of an internal combustion engine, and more particularly to a technique for preventing the overcooling and freezing of the secondary gas.
There is proposed an intake device of an internal combustion engine, having a gas passage for recirculating/adding a secondary gas (such as blowby gas, EGR gas or secondary air) to engine intake for exhaust gas purification or idle control. In the above proposed intake device, it is desired that the secondary gas be prevented from becoming overcooled and frozen even under cold engine conditions or under cold climate conditions. Especially when used in an in-line multi-cylinder internal combustion engine that is horizontally mounted on a vehicle with its intake situated toward a vehicle front side and its exhaust situated toward a vehicle rear side, at least part of the secondary gas passage lies on the engine intake side, i.e., the vehicle front side. The secondary gas thus tends to get cooled under the influence of a driving wind blowing from the vehicle front side. In order to solve this problem, Japanese Laid-Open Patent Publication No. 2000-274223 proposes the arrangement of the secondary gas passage partly adjacent to an engine coolant line so as to prevent the overcooling of the secondary gas by heat conduction from the engine coolant line to the secondary gas passage.